This invention relates to a switching device for manually or automatically selecting a certain signal among a plurality of signals generated by a plurality of sensors. Specifically, this invention relates to oximeters used to generate a representation of oxygen saturation levels in arterial blood flow in a patient.
The use of oximeters is conventional in the medical field. Oximeters are used in the operating room (OR) and the intensive care unit (ICU), as well as in other applications, to provide information regarding the oxygen level in a patient""s blood.
In normal use, the oximeter is made up of an powered analyzer section electrically connected to a sensor. In a conventional pulse oximeter, the sensor has a light emitting diode (LED) mounted on one side of the patient""s extremity, such as a finger, and a phototransistor receptor mounted on the other side. The LED sends pulses of light, in a known wavelength, into the finger. The receptor receives the light that is transmitted through the tissue and converts it to an electrical signal. There are also conventional sensors that generate a signal on the reflected light rather than transmitted light. In any event, the electrical signal is returned to the analyzer section where it is converted to a read-out which may be graphical or numerical and may be printed or displayed on a screen (CRT).
It is especially important to maintain a sterile field in the OR and the ICU. The equipment used in these locations should be sterile, also. The oxygen level in the patient""s blood is constantly monitored to determine the patient""s well being in both these settings. In certain situations in the OR, during surgery, blood flow in a particular part of the body may be interrupted or shunted into other fields. Such an event may cause the interruption of the oximeter readings, if the sensor is located on an extremity in the affected part of the body. To immediately reestablish this vital information, the sterile field may be invaded to place another sensor on the body or to move the affected sensor to another suitable location on the patient.
This situation may also occur in the ICU. Also, in the ICU the patient may cause the sensor to become dislodged through body movement. Of course, there are other mechanical reasons that a sensor may malfunction and require replacement.
This important information concerning the patient""s oxygen blood level is lost during the period of time required to position a new oximeter and hook up another sensor.
Thus, what is needed in the art is an apparatus that will provide continuous blood oxygenation readings without disturbing the patient or the sterile field when blood flow to a particular part of the body is interrupted or a sensor fails.
Mannheimer, U.S. Pat. No. 5,842,982, discloses a neonatal pulse oximeter sensor for application to the foot of a baby.
Ivers et al, U.S. Pat. No. 5,339,810 and Kaestle et al, U.S. Pat. No. 5,776,059 show pulse oximetry sensors for the finger of a patient.
Sensors may be placed on any part of the anatomy where there is a good blood flow that can be impinged by a light source, including the fingers, toes, earlobes, and nares, among others.
The conventional oximeter or the analyzer section, per se, has software, based on the Lambert-Beer equations, which converts the incoming signal from the sensor to a usable representation. The representation may take any desired form, both digital and analog.
A switching device interposed between an oximeter and a plurality of photosensors located on various body extremities. The switching device may be operated in a manual mode wherein each photosensor may be individually selected to provide the input signal to the oximeter. The switching device may also be operated in an automatic mode wherein the switching device scans the incoming signals from the different photosensors and forwards the best, strongest or least distorted signal to the oximeter. The device prevents the loss of oximetery information due to interrupted blood flow in a particular part of the body or the failure of a sensor.
It is an objective of this invention to provide an oximeter having an array of sensors connected to different parts of the patient""s body to continuously generate blood oxygenation information in the event blood supply is interrupted in a particular part of the body or a sensor malfunctions.
It is another objective of this invention to provide a switching device interposed between the array of sensors and the analyzer section for selection of a particular incoming signal from one of the sensors.
It is yet another objective of this invention to provide the switching device with a manual mode and an automatic mode of operation.
Other objectives and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The switching device of this invention need not be restricted to pulsoximetry but can be used in other general measuring systems in which plural sensors are arrayed with a single display mechanism. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.